We often hear people ask about molecular hydrogen.
They think it's some sort of exotic new thing with no direct connection to their metabolism. Years ago I listened as Tyler Lebaron talked about H2 being there in the beginning: at the beginning of life. So this quote from a study we located makes a lot of sense and may reassure the people who regard H2 as something new, alien, or exotic.
"Researchers at the Heinrich Heine University Düsseldorf (HHU) have reconstructed the metabolism of the last universal common ancestor, LUCA. They found that almost all chemical steps used by primordial life to piece together the molecular building blocks of cells are energy releasing reactions. This identified the long-sought source of energy needed to drive these reactions forward, which has been hiding in plain sight. The energy required to synthesize the building blocks of life comes from within metabolism itself, as long as one essential starting compound is included. The secret ingredient that releases the energy from within at life's origin is the cleanest, greenest, newest and oldest of all energy carriers: Hydrogen gas, H2."